/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

package util

import (
	"crypto/rand"
	"fmt"
	"io"
	"time"
	"math/big"

	gp "google/protobuf"

	"golang.org/x/crypto/sha3"
)

// ComputeCryptoHash should be used in openchain code so that we can change the actual algo used for crypto-hash at one place
func ComputeCryptoHash(data []byte) (hash []byte) {
	hash = make([]byte, 64)
	sha3.ShakeSum256(hash, data)
	return
}

// GenerateUUID returns a UUID based on RFC 4112 returning the generated bytes
func GenerateBytesUUID() []byte {
	uuid := make([]byte, 16)
	_, err := io.ReadFull(rand.Reader, uuid)
	if err != nil {
		panic(fmt.Sprintf("Error generating UUID: %s", err))
	}

	// variant bits; see section 4.1.1
	uuid[8] = uuid[8]&^0xc0 | 0x80

	// version 4 (pseudo-random); see section 4.1.3
	uuid[6] = uuid[6]&^0xf0 | 0x40

	return uuid
}

// GenerateUUID returns a UUID based on RFC 4112 returning a big.Int
func GenerateIntUUID() *big.Int {
	uuid := GenerateBytesUUID()
	z := big.NewInt(0)
	return z.SetBytes(uuid)
}

// GenerateUUID returns a UUID based on RFC 4112
func GenerateUUID() string {
	uuid := GenerateBytesUUID()
	return fmt.Sprintf("%x-%x-%x-%x-%x", uuid[0:4], uuid[4:6], uuid[6:8], uuid[8:10], uuid[10:])
}

// CreateUtcTimestamp returns a google/protobuf/Timestamp in UTC
func CreateUtcTimestamp() *gp.Timestamp {
	now := time.Now().UTC()
	secs := now.Unix()
	nanos := int32(now.UnixNano() - (secs * 1000000000))
	return &(gp.Timestamp{Seconds: secs, Nanos: nanos})
}

//name could be ChaincodeID.Name or ChaincodeID.Path
func GenerateHashFromSignature(path string, ctor string, args []string) []byte {
	fargs := ctor
	if args != nil {
		for _, str := range args {
			fargs = fargs + str
		}
	}
	cbytes := []byte(path + fargs)

	b := make([]byte, len(cbytes))
	copy(b, cbytes)
	hash := ComputeCryptoHash(b)
	return hash
}

